The flame-retardant mixture Firemaster 550 is commonly found in household dust, but the physiological effects of its components at relevant exposure levels aren’t known. An animal study conducted by NIEHS grantees shows that perinatal exposure to the flame-retardant mixture is associated with endocrine disrupting effects. The researchers observed weight gain, early onset of puberty, and cardiovascular health effects at levels that are relevant to human exposure and lower than the no observable adverse effects level reported by the manufacturer.

The researchers evaluated the effects of FM 550 in rats exposed to 100 or 1000 micrograms of the flame-retardant per day during gestation and lactation. They found that the components of Firemaster 550 accumulated in tissues of exposed mice as well as their offspring and induced metabolic syndrome characteristics in the offspring. They observed higher levels of the thyroxine thyroid hormone and reduced hepatic carboxylesterease activity in the exposed mice. The offspring exhibited advanced female puberty, weight gain, male cardiac hypertrophy, and problems with exploratory behaviors. The researchers say that their findings reveal that the flame retardant may affect growth and neurodevelopment and shows the need for more research into the mechanisms involved and human exposure levels.